To attain stable micromachining, a precision apparatus, such as a semiconductor manufacturing apparatus, must be maximally insulated from vibration conducted from the external environment. Therefore, such a precision apparatus needs to be mounted on an anti-vibration apparatus. In particular, an anti-vibration apparatus in a semiconductor exposure apparatus is demanded to realize, with good balance, external vibration insulation performance, and performance to suppress internal vibration generated upon activating a substrate stage, because it continuously moves at a high speed.
In response to such a demand, recently, an active anti-vibration apparatus is being used. The active anti-vibration apparatus controls vibration by driving an actuator in accordance with a detection signal output from a vibration sensor. The active anti-vibration apparatus has both vibration insulation performance and vibration suppression performance.
Japanese Patent Laid-Open No. 10-256144 discloses a typical arrangement example of an anti-vibration apparatus. In Japanese Patent Laid-Open No. 10-256144, an acceleration sensor is used as a vibration sensor, which detects vibration of a base as a vibration removal target, and an air spring is used as an actuator which drives the base. The acceleration sensor is so installed as to align its detection axes along the horizontal and vertical directions, and to detect the accelerations of the base in the horizontal and vertical directions. The air spring supports the base so as to match its thrust generation axes with the horizontal and vertical directions, and to generate the base thrusts in the horizontal and vertical directions. The air spring is driven in accordance with compensation values obtained by appropriately compensating detection signals of the acceleration sensor in the horizontal and vertical directions. Executing such a so-called vibration feedback operation effectively suppresses vibration of the base.
In recent years, an exposure apparatus used to manufacture a semiconductor device, a liquid crystal panel, or a magnetic head is being improved by various methods to cope with demands for a higher speed and accuracy. In particular, to meet these demands, it is very important for a structure to be free of vibration. Either of structure vibration generated upon driving an original stage or a substrate stage, and that conducted from the installation floor, must be sufficiently reduced.
A scan exposure apparatus, which drives both an original and a substrate using stages, may adopt the following arrangement. That is, an original (or projection lens) and a substrate are mounted on separate structures to separately remove vibrations acting upon driving respective stages, and an active anti-vibration apparatus (a so-called active damper) supports the structures. Alternatively, three components, i.e., an original, a substrate, and a projection lens are mounted on separate structures, and an active damper supports the structures. Such an active damper is generally so controlled as to independently remove vibrations of a first structure having an original stage (or a projection lens) and a second structure having a substrate stage. Therefore, control of the relative positional relationship between the structures, i.e., the positional relationship between the original (or projection lens) and the substrate is often unsatisfactory, resulting in an exposure failure.
Conventionally, the positional relationship between a projection lens and a substrate is generally corrected by a substrate stage alone. The exposure accuracy of this structure greatly depends on the control performance of the substrate stage.